Abstract

Background: Achieving a healthy weight is recommended for all breast cancer survivors. Previous research on postdiagnosis weight change and mortality had conflicting results.

Methods: We examined whether change in body weight in the 18 months following diagnosis is associated with overall and breast cancer–specific mortality in a cohort of n = 12,590 stage I–III breast cancer patients at Kaiser Permanente using multivariable-adjusted Cox regression models. Follow-up was from the date of the postdiagnosis weight at 18 months until death or June 2015 [median follow-up (range): 3 (0–9) years]. We divided follow-up into earlier (18–54 months) and later (>54 months) postdiagnosis periods.

Results: Mean (SD) age-at-diagnosis was 59 (11) years. A total of 980 women died, 503 from breast cancer. Most women maintained weight within 5% of diagnosis body weight; weight loss and gain were equally common at 19% each. Compared with weight maintenance, large losses (≥10%) were associated with worse survival, with HRs and 95% confidence intervals (CI) for all-cause death of 2.63 (2.12–3.26) earlier and 1.60 (1.14–2.25) later in follow-up. Modest losses (>5%–<10%) were associated with worse survival earlier [1.39 (1.11–1.74)] but not later in follow-up [0.77 (0.54–1.11)]. Weight gain was not related to survival. Results were similar for breast cancer–specific death.

Conclusion: Large postdiagnosis weight loss is associated with worse survival in both earlier and later postdiagnosis periods, independent of treatment and prognostic factors.